The City of London police reports that bike thefts increased 25 percent year on year for the period April 1 to June 30.

To help combat the tide of light-fingered scumbags swiping bikes, the police have produced two videos and a comprehensive web page showing you how easy it is for some locks to be cut and detailing the best way to stop it from happening to you.

As you can see in this video, an inexpensive cable lock can be cut in seconds.

The City of London police’s cycling expert, PCSO Scott Green, talks about some of the security options here:

The most useful part of the campaign is a comprehensive guide to choosing and using a lock. Key points from the guide include:

Get your bike on the Bike Register so that it is more likely to be recovered if it is stolen.

Store your bike inside overnight if possible.

On the street, lock your bike to a proper bike stand, and in a place where it can be seen.

Lock your frame and both wheels to an immovable object.

Use a good quality lock. Spend 20 percent of the value of your bike on a lock and use two different locks when leaving the bike for any length of time.

If using a chain lock, make sure it’s not resting on the ground where it can be more easily smashed open.

Fill a D lock with frame and wheels and use one that’s as small as practicable to stop thieves using bars or jacks to lever it open.

Point your D-locks lock mechanism down so thieves can’t pour things into it such as glue which forces you to leave the bike for them to attack the lock later.

I am pretty lucky as I work in a very secure area which has cameras watching the bikes, at home I built a key secured 7ft by 5ft bike shed, and bought off a local fabrication place a galvanized bike stand and coach bolted it to the flags, I then have two bike locks wrapping up my three bikes one of them locks is sold secure the other is just a chain wrap around...I put pipe lagging around the bike stand and the metal parts of the lock also..... I'm pretty confident mine are safe.

Yes, they're different.
I asked a Met policeman doing bike marking that same question, and he said that the Met use bike register, not immobilise.
Apparently it's because bike register uses a tamper proof (supposedly) marker, whereas immobilise just uses the frame number, which for some reason isn't a good enough identifier for them.